Speed increasing combination of stabilizers for radiographic elements

ABSTRACT

A RADIOGRAPHIC ELEMENT, WHICH COMPRISES A SUPPORT HAVING THEREON AT LEAST ONE SILVER HALIDE LAYER, WHEREIN SAID HALIDE COMPRISES AT LEAST ABOUT 50 MOLE PERCENT CHLORIDE, A SULFOCATECHOL AND A TETRAZAINDENE, SHOWS AN INCREASE IN SPEED. IN A PREFERRED EMBODIMENT SAID ELEMENT HAS A TOTAL SILVER COVERAGE OF AT LEAST ABOUT 100 MG. PER SQUARE FOOT PER SILVER HALIDE LAYER.

United States Patent 3,671,258 SPEED INCREASING COMBINATION OF STABI- LIZERS FOR RADIOGRAPHIC ELEMENTS Robert C. Taber, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed Jan. 11, 1971, Ser. No. 105,636

Int. Cl. G03c 1/28 US. Cl. 96107 19 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to radiographic materials. In one aspect, this invention relates to radiographic materials evidencing substantial improvements in speed and a means of processing the radiographic materials.

It is known that silver chlorobromide emulsions Wherein bromide is present at a greater mole percent than chloride, are generally more sensitive than emulsions in which the chloride predominates. Hence, the preference for the former emulsions in the field of radiography where speed can be an extremely critical factor.

It is also well known that silver chloride fixes faster than silver bromides.

In recent years, the use of roller transport machines has come into vogue. Through the employment of such transport systems the time of processing radiographic elements has been reduced to minutes and often reduced to as short a time as below about a minute.

In attempts to further increase the speed of existing machine processes, such as by raising processing and drying temperatures, there is generally obtained a product which sulfers from a substantial reduction in the sensitometric properties of the films.

One means of increasing the speed of the machine processing systems would be to employ radiographic elements comprising silver halide which would fix out rapidly, such as, for example, those elements containing a silver halide wherein the halide comprises a major amount of chloride. However, such silver halides have not heretofore been suitably utilized in radiographic elements due to their substantial reduced senstivity as compared with radiographic silver halide emulsions in which the halide is predominantly bromide. The art would greatly benefit should there be discovered a means of increasing the speed of silver halides, adapted for radiography, wherein the halide comprises a major portion of chloride.

It is further known that many photographic emulsions which have been greatly sensitized have a tendency to CC I evidence substantial fog levels, a condition which is generally not tolerable in the field of radiography. The fog may arise during storage or upon development during which some unexposed silver halide grains are developed. A significant contribution would be made should a substantial increase in the speed be obtained for silver halides adapted for radiography, wherein the halide comprises a major portion of chloride. It is additionally highly desirable to obtain the speed increases without a concomitant detrimental effect on other sensitometric properties, such as, for example, a degradation in contrast or an increase in fog.

It is known to incorporate sulfocatechols in radiographic emulsions, for example, see Kennard and Russell, US. Pat. 3,236,652, issued Feb. 22, 1966. Kennard et al. employed the sulfocatechols as stabilizers against fog and for stabilizing the speed and contrast of sensitized photographic emulsions.

It is also known to use tetrazaindenes in silver halide emulsions as stabilizers against fog and for stabilizing the sensitometric properties of the emulsion. The use of tetrazaindenes as stabilizers is described, for example, in Carrol et al. US. Pat. 2,716,062 issued Aug. 23, 1965; Knott US. Pat. 2,933,388 issued Apr. 13, 1960; Tinker et al. US. Pat. 2,835,581 issued May 20, 1958, and Heimbach US. Pat. 2,444,605 issued July 6, 1948.

Although it is known to add either a sulfocatechol or a tetrazaindene to photographic elements, it has not been taught heretofore that one may advantageously utilize both a tetrazaindene and a sulfocatechol in order to obtain an unexpectedly improved radiographic element.

SUMMARY OF THE INVENTION In accordance with this invention there are provided radiographic elements which exhibit marked improvements in speed and which can be advantageously employed in rapid processing machines wherein the silver halide is very rapidly fixed. The radiographic element comprises a support, at least one silver halide layer wherein the halide comprises a major portion of chloride, and the combination of a tetrazaindene with sulfocatechol.

It is accordingly an object of this invention to provide a fast radiographic silver halochloride element.

It is another object to provide a radiographic silver halide element wherein the unexposed silver halide will rapidly fix during processing.

It is a further object of the invention to provide a silver halide emulsion wherein the halide comprises at least about 50 mole percent chloride.

It is yet another object to provide a rapid method of processing said radiographic elements and emulsions.

Other objects of this invention will become obvious to those skilled in the art from that which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, the above and other objects are attained by providing a radiographic element comprising a support having thereon at least one silver halide layer, said halide comprising at least about 50 mole percent chloride, .fiaid element containing atetrazaindene.

wherein Z represents a hydroxyl or thiol group R can be hydrogen, alkyl group including substituted alkyl groups, e.g. methyl, ethyl, propyl, isopropyl, butyl,.amyl, and the like, benzyl, phenethyl and the like; cycloalkyl, e.g., cyclopentyl, cyclohexyl, and the like; aryl including substituted aryl groups e.g., phenyl, naphthyl, diphenyl, and the like, tolyl, chlorophenyl, etc.; a heterocyclic radical, e.g., pyridyl, furyl, pyrryl, pyrazolyl, and the like; CH P wherein P can be a halogen atom, e.g., chlorine, bromine, etc., or a hydroxyl group; an alkylthio, including substituted alkylthio e.g., methylthio, ethylthio and the like, benzylthio; or an arylthio, e.g., phenylthio, tolylthio and the like; and each of R and R can individually be hydrogen, halogen, amino, hydroxy, carbalkoxy, e.g., carbethoxy, .carbpropoxy, and the like; alkyl including substituted alkyl, e.g., methyl, ethyl, propyl,. .isopropyl, butyl, amyl, and the like, benzyl, phenethyl,.etc.; cycloalkyl, e.g., cyclopentyl, cyclohexyl, and the, like, aryl including substituted aryl, e.g., phenyl, naphthyl, diphenyl, and the like, tolyl, chlorophenyl, p-methoxyphenyl; or a heterocyclic radical, e.g., pyridyl, fury], pyrryl, pyrazolyl, and the like.

, The tetrazaindenes may be prepared by heating ethyl acetoacetate or its homologues with an amino triazole such as, for example, 3-amino-1,2,4-triazole'or l-amino-l, 3,4triazole. The preparations are adequately described in U.S. Pats. 2,933,388, 2,716,062, 2,444,605 and 2,835,581. Illustrative of the tetrazaindenes which may be suitably employed in this invention are:

4-hydroxy-2-methyl-6-phenyl-1,3,3a,7-tetrazaindene 4-hydroxy-2,6-diphenyl-l,3,3a,7-tetrazaindene i 4-hydroxy-2-isopropyl-6-methyl-l,3,3a,7-tetrazaindene, 4-hydroxy-2,6-dimethyl-l,3,3a,7-tetrazaindene 4,6-dihydroxy-l,3,3a,7-tetrazaindene 4-.hydrQxy-6-aminq-1,3,3a,7-t razai ene 4-hydroxy-6-carbethoxy-1,3,3a,7-tetrazaindene 4-hydroxy-6 8-pyridyl -l ,3 ,3 a,7-tetrazaindene 4-hydroxy-2-cyclohexyl-6-methyl-l,3,3a,7-tetrazaindene 4-hydroxy-2 (a-furyl -6-methyl-l ,3 ,3 a,7-tetrazaindene 4-hydroXy-6-cyclohexyl-l,3,3a,7-tetrazaindene 4-hydroxy-5-cyclohexyl-6-methyl-l,3,3a,7-tetrazaindene 4-hydroxy-5-a-furyl-G-methyl-l,3,3a,7-tetrazaindene 4-hydroxy-6-methyl-5-phenyl-l,3,3a,7-tetrazaindene 6-methyl-1 3 :3 a: 7-tetrazaindene-4-thiol 6-phenyl-1 3 3a 7-tetrazaindene-4-thiol 5-bromo-6-methyl-1 3 3a 7-tetrazaindene-4-thiol 2: 6-dimethyl-1 :3 3a: 7-tetraZaindene-4-thiol 6-methyl-2-methylthio-1 :3 3a 7-tetrazaindene-4-thiol 5-ethyl-6-methyl-1 :3 3a: 7-tetrazaindene-4-thiol 5-iso-butyl-6-methyl-1 :3 3a 7-tetrazaindene-4-thiol S-phenyl-l 2 3a 4-tetrazaindene-7-thiol 6-ethyl-5-methyl-l :2 3a 4-tetrazaindene-7-thiol 5-methyl-1 :2 3a 4-tetraZaindene-7-thio1 Any of the sulfocatechols may be suitably employed in this invention. Typically, the sulfocatechols employed contain at least one sulfo radical; however, disulfocatechols can be advantageously employed.

Typical sulfocatechols which are advantageously employed in this invention have the formula:

wherein each of X and Y is a sulfo radical or a hydrogen atom, at least one of X and Y being a sulfo radical. The preferred sulfocatechols are the 3,5-disubstitute'd sulfocatechols. It is to be understood that sulfocatechols employed in this invention include the Water-soluble salts, such as, for example, the alkali metal salts and ammonium salts. The water-soluble salts are used since the salts facilitate the incorporation of the addenda into the photographic emulsions. V

Illustrative of the compounds which can be employed are '3,5'-disulfocatechol disodium salt and 4-sulfocatechol ammonium salt. The speed increasing addenda of the invention can be located in any layer of the radiographic element, for example, the speed increasing addenda can be located in an overcoat to the silver halide layer, as an undercoat to the silver halide layer or virtually any layer adjacent to the silver halide layer. The sulfocatechols and the tetrazaindenes can be located in separate layers, for example, the sulfocatechol can be located in the silver halide layer and the tetrazaindene in an overcoat layer. Preferably the tetrazaindene and the sulfocatechol are located in the same layer. In a preferred embodiment of this invention, the sulfocatechol and tetrazaindene are incorporated in the radiographic silver halide layer.

The speed increasing addenda of the invention can be addedto the radiographic silver halide emulsions utilizing any of the well known techniques in emulsion making. For example, they can vbe dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the techniques utilized to incorporate particular colorforming compounds in photographic emulsions. Techm'ques of suchtypes of incorporation are described in US. Pats. 2,322,027 and 2,801,171. Solvents employed should not evidence any harmful effects upon the emulsion and generally the solvents are preferably miscible with water. The addenda can be added before or after ripening; the tetrazaindene and sulfocatechol can be added together or separately. Preferably the addenda should be added to the silver halide emulsion (or any other layer of the element) prior to coating and after chemical sensitization.

The radiographic material .can comprise a support bearing a silver halide emulsion only on one side. It is preferred, however, to coat the silver halide emulsion on both sides of the support. Hence, in a preferred embodiment of this invention radiographic material is provided comprising a support bearing on both sides a hydrophilic, and preferably a gelatino silver halide emulsion layer wherein the halide comprises at least about 50 mole percent chloride and incorporated in said emulsion a speed increasing combination comprising a tetrazaindene and a sulfocatechol. In another preferred embodiment the radiographic element has a total silver coverage of at least about 200 mg. per square foot. In still another embodiment of this invention the radiographic element has a total silver coverage of at least about 100 mg. per square foot per radiographic silver halide layer.

The tetrazaindene and sulfocatechol can be present in a wide range of concentrations. The concentrations at which the speed increasing properties become evident can be determined by means well known in the art. In a preferred embodiment of this invention, it has been found advantageous to utilize about 0.2 to about grams of tetrazaindene per silver mole and about 0.5 to about grams of sulfocatechol per silver mole. It should be understood, however, that concentrations outside those recited above may be suitably employed.

The halide for the radiographic silver halide advantageously comprises at least about 50 mole percent chloride, the remainder being bromide with or without iodide. In a preferred embodiment, the halide comprises from about 60 to 70 mole percent chloride, 0 to 10 percent iodide and the remainder being bromide. In another pre- 6 incorporated therein a speed increasing combination comprising a tetrazaindene and a sulfocatechol. An especially suitable photographic gelatino silver halide emulsion comprises a sulfur-gold silver chloride emulsion containing 4-hydroxy-6-methyl-1,3,3a,7- and 3,5-disulfocatechol disodium salt.

This invention can be further illustrated by the following examples of preferred embodiments thereof, although it will be understood that these examples are included merely for illustrating this invention.

Examples 1-5 In a radiographic sulfur-gold sensitized gelatin-silver chlorobromide emulsion comprising -65 mole percent chloride and mole percent bromide is incorporated 3,5-disulfocatechol disodium salt in an amount of 2.61 grams per mole of silver and 4-hydroxy 6- methyl- 1,3,3a,7-tetrazaindene in an amount of 1.75 grams per mole of silver. Three similar emulsions are prepared with the exception that other compounds which are substantially equivalent in the prior art, i.e., they are all known fog inhibiting agents, are substituted for tetrazaindene. The compounds and their amounts are described in Table I.

A final control emulsion is prepared. The control emulsion does not contain tetrazaindene.

The emulsions are coated on a polyethylene terephthalate film at 137 mg. per square foot per side and divided into separate equal portions.

A portion of the radiographic elements are exposed in an Eastman 1B Sensitometer and developed for six minutes in a p-methylaminophenol-hydroquinone developer. The second portion of emulsions are stored for one week at 120 F. and relative humidity and then similarly exposed and developed.

The results are summarized in Table I.

3,5-disulfocatechol disodium salt. 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene. 2,4rdrhydroxy-6-methyl-l,3a,7-triazaindcne. 5-am1no2(p-carboxyphenyl)-7-hydroxy-l,2,3,4,6-pentazaindene. Benzothiazole methiodide.

ferred embodiment, the halide comprises 65 mole percent chloride and 35 mole percent bromide.

Processing of the radiographic elements of this in vention can be effected in a variety of ways including the multi-tank manual methods. In accordance with an embodiment of this invention, however, the full advantage of this invention is realized when the radiographic elements are processed in a fast continuous machine processing system wherein the radiographic element is processed by passing through rollers or otherwise in one continuous motion by transporting it into, through and out of at least one processing solution in the manner shown, for example, by U.S. Pats. 3,025,779 of Russell and Kunz issued Mar. 20, 1962; 3,078,024 of Sardeson issued Feb. 19, 1963; 3,122,086 of Fitch issued Feb. 25, 1964; 3,149,551 of Cramer issued Feb. 22, 1964; 3,156,173 of Meyer issued Nov. 10, 1964; and 3,224,356 of Fleisher and Hixon issued Feb. 21, 1965. A typical roller type processing apparatus employed in the fast processing of X-ray materials is described in Belgian Pat. 700,301 issued Aug. 31, 1967, to Barnes et al.

In another embodiment of this invention there is provided a hydrophilic colloid containing and preferably gelatino silver halide emulsion wherein the halide comprises at least about 50 mole percent chloride having Example 2 which shows over a 3-fold increase in speed clearly illustrates the unexpected feature of this invention.

Examples 35 illustrates that the similar compounds or compound known to behave as fog inhibitors as does tetrazaindene, do not produce the same speed effects when combined with sulfocatechol in a radiographic element.

The silver halide emulsions used with this invention can be unwashed or washed to remove soluble salts. In the latter case the soluble salts are removed by chillsetting and leaching or the emulsion can be coagulation washed, e.g. by the procedures described in Hewitson et al. U.S. Pat. 2,618,556 issued Nov. 18, 1952; Yutzy et al. U.S. Pat. 2,614,928 issued Oct. 21, 1952; Yackel U.S. Pat. 2,565,418 issued Aug. 21, 1951; Hart et al. U.S. Pat. 3,241,969 issued Mar. 22, 1966; and Waller et al. U.S. Pat. 2,489,341 issued Nov. 29, 1949.

The emulsions used with this invention can be sensitized with chemical sensitizers, such as with reducing agents; for example, sulfur, selenium or tellurium compounds; gold, platinum or palladium compounds; or combinations of these. Suitable procedures for sensitization are described in Sheppard et al. U.S. Pat. 1,623,499 issued Apr. 5, 1927; Waller et al. U.S. Pat. 2,399,083

7 issued Apr. 23, 1946; McVeigh U.S. Pat. 3,297,447 issued Jan. 10, 1967; and Dunn U.S. Pat. 3,297,446 issued Jan. 10, 1967.

The silver halide emulsions used with this invention can contain, in addition to the speed increasing addenda of this invention, speed increasing compounds such as polyalkylene glycols, cationic surface active agents and thioethers or combinations of these as described in Piper U.S. Pat. 2,886,437 issued May 12, 1959; Dann et al. U.S. Pat. 3,046,134 issued July 24, 1962; Carroll et al. U.S. Pat. 2,944,900 issued July 12, 1960; and Goffe U.S. Pat. 3,294,540 issued Dec. 27, 1966.

. The silver halide emulsions used in the practice of this invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers each used alone or in combination include thiazolium salts described in Brooker et al. U.S. Pat. 2,131,038 issued Sept. 27, 1938, and Allen et al. U.S. Pat. 2,694,716 issued Nov. 16, 1954; the mercury salts as described in Allen et al. U.S. Pat. 2,728,663 issued Dec. 27, 1955; the urazoles described in Anderson et al. U.S. Pat. 3,287,135 issued Nov. 22, 1966; the oximes described in Carroll et al. British Pat. 623,448 issued May 18, 1949; nitron; nitroindazoles; the mercaptotetrazoles described in Kendall et al. U.S. Pat. 2,403,927 issued July 16, 1946; Kennard et al. U.S. Pat. 3,226,897 issued Aug. 16, 1966, and Luckey et al. U.S. Pat. 3,397,987 issued Aug. 20, 1968; the polyvalent metal salts described in Jones U.S. Pat. 2,839,405 issued June 17, 1958; the thiuronium salts described in Herz et al. U.S. Pat. 3,220,839 issued Nov. 30, 1965; the palladium, platinum and gold salt described in Trivelli et al. U.S. Pat. 2,566,263 issued Aug. 28, 1951, and Yutzy et al. U.S. Pat. 2,597,915 issued May 27, 1952.

The photographic elements of this invention can contain incorporated developing agents such as hydroquinones, catechols, aminophenols, 3 pyrazolidones, ascorbic acid and its derivatives, reductones and phenylenediamines. Combinations of developing agents can be employed in the practice of the invention. The developing agents can be in a silver halide emulsion and/or in another suitable location in the photographic element. The developing agents can be added from suitable solvents or in the form of dispersions as described in Yackel U.S. Pat. 2,592,368 issued Apr. 8, 1952 and Dunn et al., French Pat. 1,505,778.

The photographic and other hardenable layers used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as the aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguar gum and the like.

The photographic emulsions and elements described in the practice of this invention can contain various colloids alone or in combination as vehicles, binding agents and various layers. Suitable hydrophilic materials include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers and the like.

The described photographic emulsion layers and other layers of a photographic element employed in the practice of this invention can also contain alone or in combination With hydrophilic, water permeable colloids, other synthetic polymeric compounds such as dispersed vinyl compounds such as in latex form and particularly those which increase the dimensional stability of the photographic materials. Suitable synthetic polymers include those described, for example, in Nottorf U.S. Pat. 3,142,568 issued July 28, 1964; White U.S. Pat. 3,193,386 issued July 6, 1965; Houck et al. U.S. Pat. 3,062,674 issued Nov. 6, 1962; Houck et al. U.S. Pat. 3,220,844 issued Nov. 30, 1965; Ream et al. U.S. Pat. 3,287,289 issued Nov. 22, 1966; and Dykstra U.S. Pat. 3,411,911 issued Nov. 19, 1968; particularly effective are those Water insoluble polymers of alkyl acrylates and methylacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, those which have crosslinking sites which facilitate hardening or curing, those having recurring sulfobetaine units as described in Dykstra Canadian Pat. 774,054.

The photographic elements used with this invention can contain antistatic or conducting layers, such layers can comprise soluble salts, e.g. chlorides, nitrates, etc., evaporated metal layers, ionic polymers such as those described in Minsk U.S. Pat. 2,861,056 issued Nov. 18, 1958 and Sterman et al., U.S. Pat. 3,206,312 issued Sept. 14, 1965 or insoluble inorganic salts such as those described in Trevoy U.S. Pat, 3,428,451 issued Feb. 18, 1969.

In addition, the photographic layers and other layers of a photographic element employed and described herein can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as Well as glass. Typically, a flexible support is employed.

The photographic layers employed in the practice of this invention can contain plasticizers and lubricants such as polyalcohols, e.g. glycerin and diols of the type described in Milton et al., U.S. Pat. 2,960,404 issued Nov. 1, 1966; fatty acids or esters such as those described in Robijns U.S. Pat. 2,588,765 issued Apr. 11, 1952, and Duane U.S. Pat, 3,121,060 issued Feb. 11, 1964; and silicone resins such as those described in DuPont British Pat. 955,061 issued Apr. 15, 1964.

The photographic layers employed in the practice of this invention can contain surfactants such as saponin; anionic compounds such as the alkyl aryl sulfonates described in Baldsiefen U.S. Pat. 2,600,831 issued June 17, 1952; amphoteric compounds such as those described in Ben-Ezra U.S. Pat. 3,133,816 issued May 19, 1964; and water soluble adducts of glycidol and an alkyl phenol such as those described in Olin Mathieson British Pat. 1,022,- 878 issued Mar. 16, 1966.

The photographic elements employed in the practice of this invention may contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads of the type described in Jelley et al., U.S. Pat. 2,992,101 issued July 11, 1961 and Lynn U.S. Pat. 2,701,245, issued Feb. 1, 1955.

The various layers, including the photographic layers, employed in the practice of this invention can contain light absorbing materials and filter'dyes such as those described in SaWdey U.S. 'Pat. 3,253,921 issued May 31, 1966; Gaspar U.S. Pat. 2,274,782 issued Mar. 3, 1942; Silberstein et al. US. Pat. 2,527,583 issued Oct. 31, 1950, and VanCampen U.S. Pat. 2,956,879 issued Oct. 18, 1960. If desired, the dyes can be mordanted, for example, as described in Milton et al. U.S. Pat. 3,282,699 issued Nov. 1, 1966.

The dyes and other addenda used in the practice of this invention can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures including those described in Collins et al., U.S. Pat. 2,912,343 issued Nov. 10, 1959; McCrossen et al., U.S. Pat. 3,342,605 issued Sept. 19, 1967; Audran U.S. Pat. 2,996,287 issued Aug. 15, 1961 and Johnson et al., U.S. Pat. 3,425,835 issued Feb. 4, 1969.

The photographic layers used in the practice of this i11- vention can be coated by various coating procedures including dip coating, air knife coating, curtain coating, or extrusion coating using hoppers of the type described 9 in Beguin U.S. Pat. 2,681,294 issued June 15, 1954. If desired, two or more layers may be coated simultaneously by the procedures described in Russell U.S. Pat. 2,761,791 issued Sept. 4, 1956 and Wynn British Pat. 837,095. This invention also can be used for silver halide layers coated by vacuum evaporation as described in British Pat. 968,- 453 and LuValle et al. U.S. Pat. 3,219,451 issued Nov. 23, 1965.

Photographic elements prepared according to this invention can be processed by various methods including processing in alkaline solutions containing conventional developing agents such as hydroquinones, catechols, aminophenols, 3-pyrazolidones, phenylenediamines, ascorbic acid derivatives, hydroxylamines, hydrazines, reductones and the like; web processing such as described in Tregillus et al. U.S. Pat. 3,179,517 issued Apr. 20, 1965; stabilization processing as described in Russell et al. Stabilization Processing of Films and Papers, PSA Journal, vol. 16B, August 1950; monobath'processing as described in Levy Combined Development and Fixation of Photographic Images with Monobaths, Phot. Sci. and Eng., vol. 2, No. 3, October 1958, and Barnes et al. U.S. Pat. 3,392,019 issued July 9, 1968. If desired, the photographic elements of this invention can be processed in hardening developers such as those described in Allen :et al. U.S. Pat. 3,232,761 issued Feb. 1, 1966.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

There is claimed:

1. A radiographic element comprising a support having thereon at least one silver halide layer, said halide comprising at least about 50 mole percent chloride; said element containing a tetrazaindene and a sulfocatechol, said tetrazaindene being present in an amount from about 0.2 g. to about g. per mole of silver, and said sulfocatechol being present in an amount from about 0.5 g. to about g. per mole of silver.

2. A radiographic element of claim 1, wherein said element has a silver coverage of at least about 200 mg. per square foot.

3. A radiographic element of claim 2 wherein said element has a silver coverage of at least about 100 mg. per square foot per silver halide layer.

4. A radiographic element of claim 3 wherein said silver halide layer is a gelatino silver halide emulsion layer.

5. A radiographic element of claim 4 wherein said tetrazaindene and said sulfocatechol is incorporated in said gelatino silver halide emulsion layer.

6. A radiographic element as in claim 5 wherein said support bears a gelatino silver halide emulsion layer on each side.

7. A radiographic element of claim 5 wherein said tetrazainedene is 4 hydroxy 6 methyl 1,3,3a,7- tetrazaindene.

8. A radiographic element of claim 5 wherein said sulfocatechol is 3,5-disulfocatechol disodium salt.

9. A radiographic element of claim 1 wherein said tetrazaindene is a l,3,3a,7-tetrazaindene, or a 1,2,3a,4- tetrazaindene.

10. A radiographic element of claim 9 wherein said 1,3,3a,7-tetrazaindene hasthe formula:

and said 1,2,3a,4-tetrazaindene has the formula:

wherein Z is a hydroxyl or thiol group, R is hydrogen, an alkyl group, a cycloalkyl group, an aryl group, a heterocyclic radical, CH P wherein P can be a halogen atom or hydroxyl group, an alkyl thio group, or an aryl thio; and each of R and R taken individually can be hydrogen, an amino group, hydroxyl, carbal'koxy, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group.

11. A radiographic element of claim 1 wherein said sulfocatechol has the formula:

wherein each of X and Y is a sulfo radical, a water soluble salt of said sulfo radical or a hydrogen atom, at least one of X and Y being a sulfo radical or said salt of said sulfo radical.

12. A radiographic element of claim 11 wherein said sulfocatechol is a 3,5-disulfosubstituted catechol.

13. A radiographic element comprising a support having on each side thereof a gelatino silver halide emulsion layer, said halide comprising at least about 50 mole percent chloride, said element having a total silver coverage of at least about 200 mg./ift. and incorporated in said silver halide emulsion layer the combination of a tetrazaindene with a sulfocatechol, said tetrazaindene being present in an amount from about 0.2 g. to about 10 g. per mole of silver, and said sulfocatechol being present in an amount from about 0.5 g. to about 15 g. per mole of silver.

14. A radiographic element of claim 13 wherein said element has a total sil'ver coverage of at least about milligrams per square foot per silver halide layer.

15. A photographic gelatino silver halide emulsion, said halide comprising at least about 50 mole percent chloride, and incorporated in said emulsion the combination of a tetrazaindene with a sulfocatechol, said tetrazaindene being present in an amount from about 0.2 g. to about 10 g. per mole of silver, and said sulfocatechol being present in an amount from about 0.5 g. to about 15 g. per mole of silver.

16. A photographic emulsion as in claim 15 wherein said halide comprises at least about 50 mole percent chloride, 0 to 10 mole percent iodide, the remainder being b rornide.

17. A photographic emulsion as in claim 15 said emulsion being sulfur and gold sensitized.

18. A photographic sulfur-gold sensitized gelatino silver halide emulsion, said halide comprising 65 mole percent chloride and 35 mole percent bromide, said emulsion having incorporated therein 4hydroxy-6-methyl-l,3,3a,7- tetrazaindene and 3,5-disulfocatechol disodium salt, said tetrazaindene being present in an amount from about 0.2 g. to about 10 g. per mole of silver, and said sulfocatechol being present in an amount from about 0.5 g. to about 15 g. per mole of silver.

1 1 1'2 19. A photographic emulsion of claim 18 wherein said 2,955,037 101 1960 Smith L 96 .109 tetrazaindene is present in an amount of 1.75 grams per Y 2,933,388 4/ 1960 Knott'. 96-409 mole of silver and said sulfocatechol salt is present in an 2,7 16,062 8/1955 Carroll et a1. '96109 amount of 2.61 grams per mole of silver. w v i 1 4 5 1 FOREIGN PATENTS References Cited 981,470 1/1965 Great Britain 96-109 UNITED STATES PATENTS NORMAN G. TORCHINJ rimary Examiner I 3,573,056 3/1971 Baldock et a1 96109 '10 WINKELMAN, Assistant Examiner 3,411,914 11/1968 Dostes 96-409 v 7 3,236,652 2/1966 Kennard et a1. 96-109 

